KR20230034016A - Manufacturing method for Ti-6Al-4V alloy multilayer shaped structure and Ti-6Al-4V alloy multilayer shaped structure thereof - Google Patents

Abstract

The present invention relates to a method for manufacturing a Ti-6Al-4V alloy multilayer shaped structure and a Ti-6Al-4V alloy multilayer shaped structure using the same, wherein the shortcoming of a multilayer material, which has poor market competitiveness due to low productivity despite excellent mechanical properties, can be compensated for. The method for manufacturing a Ti-6Al-4V alloy multilayer shaped structure according to the present invention, which is an additive manufacturing method using laser powder bed fusion (L-PBF), comprises; a first step of providing Ti-6Al-4V alloy powder manufactured using a gas spraying method; a second step of setting process variables for laser powder bed fusion; a third step of supplying the alloy powder; a fourth step of melting the alloy powder by selectively radiating shaping light; a fifth step of forming one layer made of the Ti-6Al-4V material by cooling and solidifying the melted alloy powder; and a sixth step of making layers by repeating the third step to the fifth step until a three-dimensional shaped structure made of the Ti-6Al-4V material is completed, wherein the process variables in the fourth step are set to laser power of 240 to 350 W and a scanning speed of 1,200 to 1,800 mm/s.

Description

Manufacturing method for Ti-6Al-4V alloy multilayer shaped structure having excellent productivity and Ti-6Al-4V alloy multilayer shaped structure using the same

The present invention provides a method for manufacturing a Ti-6Al-4V alloy laminated body having excellent productivity that can compensate for the disadvantages of laminated materials having excellent mechanical properties but low productivity and poor market competitiveness, and Ti-6Al-4V alloy laminated using the same. It's about sculpture.

The Ti-6Al-4V alloy laminate is a material generally used in aerospace, medical, and turbine engine fields, and its range of use is increasing as net-shape parts can be manufactured through the additive manufacturing process. On the other hand, 3D printing using a laser or electron beam as a heat source has a problem in that production cost is high because it uses expensive powder material, but productivity is low because it takes a long time to manufacture. Therefore, the present invention is to propose a method of manufacturing a Ti-6Al-4V alloy laminated body by an additive manufacturing method by appropriately setting an additive manufacturing method in order to compensate for the low productivity mentioned as a disadvantage of the additive manufacturing method.

In the case of the prior art, as in Korean Patent Registration No. 10-1616499, it is intended to improve mechanical properties through a method of manufacturing a Ti alloy by a 3D printing method and heat treatment, and there is no mention of the lamination process variable of the Ti alloy and the invention The tensile strength of the metal molded article manufactured through the is about 570 to 650 MPa. That is, in the conventional case, in order to increase the tensile strength of Ti alloy, a heat treatment process for controlling the microstructure and precipitated phase has been performed, but the level is only about 400 to 900 MPa. Therefore, in the present invention, it is intended to propose a method for obtaining a higher level of tensile strength by adjusting only process parameters without going through a heat treatment process.

Korean Patent Registration No. 10-1616499

The present invention has been made to solve the above problems, and an object of the present invention is to provide a method for manufacturing a Ti-6Al-4V alloy laminate having high tensile strength.

In addition, an object of the present invention is to provide a method for manufacturing a Ti-6Al-4V alloy additive manufacturing method that can compensate for the low productivity mentioned as a disadvantage of the additive manufacturing method.

The technical problems to be solved by the invention are not limited to the above-mentioned technical problems, and other technical problems not mentioned will be clearly understood by those skilled in the art from the description below. You will be able to.

The manufacturing method of the Ti-6Al-4V alloy laminated sculpture according to the present invention,

In the additive manufacturing method using Laser Powder Bed Fusion (L-PBF),

A first step of providing Ti-6Al-4V alloy powder produced by a gas injection method;

A second step of setting process parameters for the laser powder sintering method;

A third step of supplying the alloy powder;

A fourth step of selectively irradiating a shaping light source to melt the alloy powder;

a fifth step of forming one layer of the Ti-6Al-4V material by cooling and solidifying the molten alloy powder;

Step 6 of repeating and stacking the steps 3 to 5 until the three-dimensional object of the Ti-6Al-4V material is completed; is made including,

The process parameters of the fourth step are characterized in that the laser power of 240 to 350 W and the scan speed of 1,200 to 1,800 mm/s are set.

By means of solving the above problems, the present invention can produce a Ti-6Al-4V alloy laminated body having high tensile strength.

In addition, the present invention can supplement low productivity, which is mentioned as a disadvantage of the additive manufacturing method.

1 is a flow chart showing a method for manufacturing a Ti-6Al-4V alloy laminated body of the present invention.
2 is a graph showing an effect of increasing productivity according to a scan speed and laser power according to an embodiment of the present invention.
Figure 3 shows the tensile strength (tensile strength) graph.
4 is a stress-strain curve of a Ti-6Al-4V alloy laminated body manufactured according to an embodiment of the present invention according to an embodiment of the present invention.
5 is an optical micrograph of a Ti-6Al-4V alloy laminated body manufactured according to an embodiment of the present invention according to an embodiment of the present invention.
6 is an X-ray CT analysis of a Ti-6Al-4V alloy laminated body manufactured according to an embodiment of the present invention according to an embodiment of the present invention.

The terms used in this specification will be briefly described, and the present invention will be described in detail.

The terms used in the present invention have been selected from general terms that are currently widely used as much as possible while considering the functions in the present invention, but these may vary depending on the intention of a person skilled in the art or precedent, the emergence of new technologies, and the like. Therefore, the term used in the present invention should be defined based on the meaning of the term and the overall content of the present invention, not simply the name of the term.

In the entire specification, when a part is said to "include" a certain component, it means that it may further include other components, not excluding other components unless otherwise stated.

Hereinafter, with reference to the accompanying drawings, embodiments of the present invention will be described in detail so that those skilled in the art can easily carry out the present invention. However, the present invention may be embodied in many different forms and is not limited to the embodiments described herein.

The specific details, including the problem to be solved, the means for solving the problem, and the effect of the invention for the present invention are included in the embodiments and drawings to be described below. Advantages and features of the present invention, and methods for achieving them, will become clear with reference to the embodiments described below in detail in conjunction with the accompanying drawings.

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings.

As shown in Figure 1, the manufacturing method of the Ti-6Al-4V alloy laminated body of the present invention can be performed as follows.

First, in the first step (S10), Ti-6Al-4V alloy powder is provided. In the first step (S10), the Ti-6Al-4V alloy powder is prepared by a gas injection method.

The Ti-6Al-4V alloy is prepared by using the Ti-6Al-4V alloy powder prepared by the gas injection method to have a particle size of 30 to 50 μm.

Next, in the second step (S20), process variables are set. The second step (S20) sets process parameters for laser powder sintering.

The process variables are controlled by setting laser power, scan speed, hatching space, and layer thickness.

The laser power is preferably 240 to 350 W. As shown in FIG. 2, when the laser power is less than 240 W, the energy is too low, so the stacking time is too long, and stacking defects such as unmelted powder are generated, resulting in problems in that the tensile strength or yield strength of the stacked object is too low. And, when the laser power exceeds 350 W, vaporization of the powder occurs and there is a possibility that the laminated object may be physically deformed.

The scan speed is preferably 1,200 to 1,800 mm/s. As shown in FIG. 2, when the scan speed is less than 1,200 mm/s, the scan speed is too low, causing a problem that the stacking time takes too long, and when the scan speed exceeds 1,800 mm/s, the applied to the powder Since the amount of energy is reduced and a stacking fault occurs along the scan direction, there is a possibility that the resulting laminated object may be physically deformed. Therefore, it is preferable to perform the above condition. That is, when the laser power is high and the scan speed is slow, the powder is vaporized while irradiating the powder with excessive energy, and there is a risk of deteriorating surface roughness and physical properties. On the other hand, when the laser power is low and the scan speed is high, energy is not irradiated and unmelted powder is formed, resulting in stacking defects. Therefore, in order to manufacture a molded body with high productivity, it is necessary to set optimal process conditions with high laser power and high scan speed.

The hatching space is an interval between laser scan paths along which the laser moves, and is preferably 50 to 100 μm. If the hatching space is less than 50 μm, productivity decreases, and if the hatching space exceeds 100 μm, the overlapping area decreases and porosity increases. Therefore, it is preferable to perform under the above conditions. do.

The layer thickness (layer thickness) is preferably 20 to 40 ㎛. If the layer thickness is less than 20 μm, there is a risk of vaporization of the powder due to excessive heat input, and if the layer thickness exceeds 40 μm, heat transfer may not be performed properly and the unmelted powder may increase Since the probability is high, it is preferable to perform under the above conditions.

The hatching space and layer thickness, which are related to the size of the laser beam, determine the size of the molten pool. The above process variables can be stacked by selecting process conditions with excellent productivity without deteriorating the physical properties of the molded body.

Higher productivity requires higher energy densities using higher laser powers and scan speeds. Since the 1980s, laser power and scan speed have generally been limited to less than 200 W and 1200 mm/s, respectively, due to operational stability and limited specifications of equipment. As shown in FIG. 2, efforts have been made to obtain appropriate mechanical properties by controlling various process variables under the laser power and scan speed conditions of the present invention.

Build rate (VB), a representative indicator of the productivity of the L-PBF process, is determined by the following equation (1).

VB = VS X Δy X Δz (1)

(Where VS is the scan speed, Δy is the increase in hatching space, and Δz is the increase in layer height)

The productivity of L-PBF parts is affected by volume according to the control of process parameters, and the scan speed is the most important parameter for improving productivity.

Next, in the third step (S30), the alloy powder is supplied. After setting the process parameters in the second step (S20), the Ti-6Al-4V alloy powder is supplied to the laser.

Next, in the fourth step (S40), the alloy powder is melted. In the fourth step (S40), the alloy powder is melted by selectively irradiating a shaping light source.

Next, in the fifth step (S50), one layer of the Ti-6Al-4V material is formed. In the fifth step (S50), one layer of the Ti-6Al-4V material is formed while being solidified at room temperature (24 to 26 °C) in an Ar gas atmosphere.

Next, the sixth step (S60), the third step (S30) to the fifth step (S50) are repeated and laminated. In the sixth step (S60), the third step (S30) to the fifth step (S50) are repeatedly laminated until the three-dimensional sculpture of the Ti-6Al-4V material is completed.

The Ti-6Al-4V alloy laminated body of the present invention is characterized in that it is produced by the Ti-6Al-4V alloy laminated body manufacturing method described above. The Ti-6Al-4V alloy laminated body manufactured according to an embodiment of the present invention is shown in FIGS. 5 and 6 .

The Ti-6Al-4V alloy laminate is characterized in that it is manufactured by controlling the laser power to 240 to 350 W during manufacture. When the laser power is less than 240 W, the energy is too low, so the laminate production time takes too long, and stacking defects such as unmelted powder are generated, resulting in problems in that the tensile strength or yield strength of the laminated body is too low, and the laser power is 350 W. When W is exceeded, vaporization of the powder occurs and there is a concern that the laminated object may be physically deformed, so it is preferable to perform the above conditions.

In addition, the Ti-6Al-4V alloy laminated body is characterized in that it is manufactured by controlling the scan speed to 1,200 to 1,800 mm / s during manufacture. When the scan speed is less than 1,200 mm/s, the scan speed is too low and the stacking time takes too long, and when the scan speed exceeds 1,800 mm/s, the amount of energy applied to the powder is reduced. Since stacking faults occur along the scan direction and there is a concern that the resulting laminated object may be physically deformed, it is preferable to perform the above condition.

In addition, the Ti-6Al-4V alloy laminate is characterized in that it is manufactured by controlling a hatching space (hatching space), which is an interval between laser scan paths in which the laser moves during manufacturing, to 50 to 100 μm. If the hatching space is less than 50 μm, productivity decreases, and if the hatching space exceeds 100 μm, the overlapping area decreases and porosity increases. Therefore, it is preferable to perform under the above conditions. do.

In addition, the Ti-6Al-4V alloy laminated body is characterized in that one layer thickness (layer thickness) of 20 to 40 ㎛ when laminated with a laser. If the layer thickness is less than 20 μm, there is a risk of vaporization of the powder due to excessive heat input, and if the layer thickness exceeds 40 μm, heat transfer may not be performed properly and the unmelted powder may increase Since the probability is high, it is preferable to perform under the above conditions.

In addition, the Ti-6Al-4V alloy laminate is characterized in that the tensile strength (tensile strength) of 1,100 to 1,200 MPa. The Ti-6Al-4V alloy laminated body manufactured according to the present invention has increased tensile strength by controlling process variables such as laser power, scan speed, hatching space, and laser thickness. Conventionally, in order to increase the tensile strength of Ti alloy, a heat treatment process for controlling the microstructure and precipitated phase was performed, but it was confirmed at a level of only about 400 to 900 MPa.

In addition, the Ti-6Al-4V alloy laminate is characterized in that the yield strength (yield strength) is 1,000 to 1,100 MPa. The Ti-6Al-4V alloy laminated body manufactured according to the present invention has increased yield strength by controlling only the process parameters without undergoing a heat treatment process.

In addition, the Ti-6Al-4V alloy laminate is characterized in that the elongation is 6% or more.

Below, tensile strength, yield strength and elongation were measured using the Ti-6Al-4V alloy laminated body manufactured by the method described above. Hereinafter, examples will be described in detail to aid understanding of the present invention. However, the following examples are merely illustrative of the contents of the present invention, but the scope of the present invention is not limited to the following examples. The embodiments of the present invention are provided to more completely explain the present invention to those skilled in the art.

Example

Ti-6Al-4V powder prepared by the gas injection method was used in the L-PBF process, and as shown in Table 1, various process parameters (laser power: 245-343 W, scanning speed: 1250-1750 mm/s, Hatching space: 70 μm, layer thickness: 30 μm) was used. The specimen designated as 'H' specimen had a support height of 30 mm, while the 'L' specimen was manufactured to have a support height of 10 mm from the plate. In the example, a tensile test was performed in an as-built state in which the heat treatment process was not attempted.

In the case of the H specimen, the energy density was the same because the laser power and scanning speed increased together. However, in the case of the L specimen, the energy density increased because the scanning speed was fixed at 1250 mm/s. After L-PBF, a stress relief treatment was performed at 720 °C for 2 hours.

sample Lower power
(W) Scanning speed (mm/s) Hatch space (㎛) Layer thickness (㎛) Energy Density
(10 ⁹ J/m3) H0 245 1,250 70 30 93.3 L0 343 1,750 70 30 93.3

comparative example

Comparative examples were molded by laser powder sintering in the same manner as the previously described examples. However, as in the process conditions of Table 2 below, a laminated object was manufactured by controlling laser power, scanning speed, hatching space, and layer thickness differently from the examples. The manufactured laminated body was manufactured with a height of 30 mm and a width of 10 mm.

sample process parameter Lower power
(W) Scanning speed (mm/s) Hatch space (㎛) Layer thickness (㎛) Case 1 Value - - - - Case 2 Value - 100 to 8000 - 50 to 200 Case 3 Value - - - - Case 4 Value - 1000 to 3000 - 50 to 200

Experimental example

(1) OM, XRD and X-ray CT analysis

For microstructure observation, cubic specimens (20 x 20 x 20 mm) were fabricated, polished and etched with Kroll solution (3 mL HNO3, 5 mL HF and 92 mL H2O) for 5-10 seconds. An optical microscope (model name: I-Scope 2001) and SEM (model name: Philips XL30S FEG) were used to observe the microstructure.

OM micrographs of the as-built Ti-6Al-4V alloy made of L-PBF are shown in FIG. 5 . In addition, X-ray CT analysis of the internal micropores measured for the H0, L0, and L2 specimens is shown in FIG. 6.

(2) Tensile strength

Tensile specimens with a total length of 75 mm, a gauge length of 25.4 mm, and a diameter of 4.75 mm were fabricated in an as-built state in which no heat treatment process was attempted. The uniaxial tensile test was performed at a strain rate of 10 ^-3 /s using a universal testing machine (MINOS-300S, MTDI, Korea).

The roughness of the surface of the tensile specimen was measured using a profilometer (Dektak 150).

sample Tensile strength (MPa) Case 1 570 to 650 Case 2 418 to 686 Case 3 600 to 900 Case 4 550 to 800 H0 1,090 L0 1,170

In general, there is no case of inventing a material having excellent tensile strength while succeeding in additive manufacturing by increasing laser power and scan speed in order to improve productivity during additive manufacturing of Ti-6Al-4V alloy. As a result of confirming the tensile strength according to the comparative example, a heat treatment process was performed to control the microstructure and the precipitated phase in order to increase the tensile strength of the Ti alloy, but it was only about 400 to 900 MPa.

As shown in Table 3 and FIG. 3, in the present invention, tensile strengths of 1,090 and 1,170 MPa were obtained by adjusting only the process parameters without going through the heat treatment process.

(3) yield strength

A tensile test was conducted in an as-built state in which the heat treatment process was not attempted, and the yield strength was measured after obtaining a stress-strain curve. Tensile specimens with a total length of 75 mm, a gauge length of 25.4 mm, and a diameter of 4.75 mm were machined according to ASTM E8/E8M. A tensile test was performed at a strain rate of 10 ^-3 /s at room temperature. After conducting the tensile test, the yield strength was measured by using a straight line in the elastic region with a 0.2% offset at the point where the strain is zero.

Table 4 and FIG. 4 show the yield strength results obtained with the specimens prepared in Examples and Comparative Examples.

sample Yield strength (MPa) Case 1 480 to 520 Case 2 - Case 3 - Case 4 520~720 H0 1,002 L0 1,050

In general, there is no case of inventing a material having excellent yield strength while succeeding in additive manufacturing by increasing laser power and scan speed in order to improve productivity during additive manufacturing of Ti-6Al-4V alloy. As a result of confirming the yield strength according to the comparative example, a heat treatment process was performed to control the microstructure and the precipitate phase in order to increase the yield strength of the Ti alloy, but it was only about 480 to 720 MPa.

As shown in Table 4, in the present invention, yield strengths of 1,002 and 1,050 MPa were obtained by adjusting only the process parameters without going through the heat treatment process.

(4) Elongation

A tensile test was conducted in an as-built state in which the heat treatment process was not attempted, and the elongation was measured after obtaining a stress-strain curve. Tensile specimens with a total length of 75 mm, a gauge length of 25.4 mm, and a diameter of 4.75 mm were machined according to ASTM E8/E8M. A tensile test was performed at a strain rate of 10 ^-3 /s at room temperature. When the break point of the stress-strain curve and a straight line with the same slope as the slope of the elastic region intersect, the value of the x-intercept (y=0) of the straight line is the elongation.

Table 5 shows the elongation results obtained with the specimens prepared in Examples and Comparative Examples.

sample Elongation (%) Case 1 20 to 25 Case 2 14-29 Case 3 - Case 4 12 to 20 H0 6.8 L0 7.5

As shown in Table 5, in the present invention, elongation rates of 6.8 and 7.5% were obtained by adjusting only the process parameters without going through the heat treatment process. Compared to Comparative Examples (cases 1 to 4), the elongation rates of Examples (H0 and L0) decreased, but in the examples, the scan speed and laser power were increased and the elongation rate was high even though heat treatment was not performed. It can be seen that the process variable condition is very beneficial.

By means of solving the above problems, the present invention can produce a Ti-6Al-4V alloy laminated body having high tensile strength.

In addition, the present invention can supplement low productivity, which is mentioned as a disadvantage of the additive manufacturing method.

As such, it will be understood that the technical configuration of the present invention described above can be implemented in other specific forms without changing the technical spirit or essential features of the present invention by those skilled in the art to which the present invention pertains.

Therefore, the embodiments described above should be understood as illustrative and not restrictive in all respects, and the scope of the present invention is indicated by the claims to be described later rather than the detailed description, and the meaning and scope of the claims and their All changes or modified forms derived from equivalent concepts should be construed as being included in the scope of the present invention.

S10. The first step to provide Ti-6Al-4V alloy powder
S20. The second step of setting process parameters for laser powder sintering
S30. The third step of supplying the alloy powder
S40. 4th step of melting the alloy powder
S50. 5th step of forming one layer of the Ti-6Al-4V material
S60. Step 6 of laminating by repeating steps 3 to 5 above

Claims (10)

In the additive manufacturing method using Laser Powder Bed Fusion (L-PBF),
A first step of providing Ti-6Al-4V alloy powder produced by a gas injection method;
A second step of setting process parameters for laser powder sintering;
A third step of supplying the alloy powder;
A fourth step of selectively irradiating a shaping light source to melt the alloy powder;
a fifth step of forming one layer of the Ti-6Al-4V material while cooling and solidifying the molten alloy powder;
Step 6 of repeating and stacking the steps 3 to 5 until the three-dimensional object of the Ti-6Al-4V material is completed; is made including,
The process parameters of the second step are characterized in that the laser power of 240 to 350 W and the scan speed of 1,200 to 1,800 mm / s are set, Ti-6Al-4V alloy laminate manufacturing method.
According to claim 1,
The process variables of the second step are,
A method for manufacturing a Ti-6Al-4V alloy laminated body structure, characterized in that a hatching space, which is an interval between laser scan paths in which the laser moves, is set to 50 to 100 μm.
According to claim 1,
The process variables of the second step are,
Method for manufacturing a Ti-6Al-4V alloy laminated body, characterized in that by setting the layer thickness (layer thickness) to 20 to 40 ㎛.
According to claim 1,
In the fifth step, the cooling and solidification is performed at 720 ° C. for 2 hours. Ti-6Al-4V alloy laminate manufacturing method.
It is manufactured by an additive manufacturing method using a laser powder bed fusion (L-PBF) method,
A Ti-6Al-4V alloy laminate, characterized in that produced by controlling a laser power of 240 to 350 W and a scan speed of 1,200 to 1,800 mm/s.
According to claim 5,
A Ti-6Al-4V alloy laminated object, characterized in that it is manufactured by controlling a hatching space, which is an interval between laser scan paths in which the laser moves, to 50 to 100 μm.
According to claim 5,
Ti-6Al-4V alloy laminated sculpture, characterized in that one layer thickness (layer thickness) during lamination is 20 to 40 ㎛.
According to claim 5,
Ti-6Al-4V alloy laminated body, characterized in that the yield strength is 1,000 to 1,100 MPa.
According to claim 5,
Ti-6Al-4V alloy laminated body, characterized in that the tensile strength is 1,100 to 1,200 MPa.
According to claim 5,
Ti-6Al-4V alloy laminated body, characterized in that the elongation is 6% or more.

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